In the realm of theoretical physics, researchers are continually pushing the boundaries of our understanding of the universe. Among them is Ilija Rakic, a researcher affiliated with the University of Cambridge, who has been delving into the intriguing behavior of black holes, particularly those that are near-extremal, meaning they have almost maximum charge or spin for their mass. His recent work, published in the journal Physical Review D, explores the quantum rate of charged particle emission from these black holes and compares it to the semi-classical Hawking rate.
Rakic’s research focuses on black holes described by the Reissner-Nordström solution, which includes electric charge, and the Kerr solution, which includes angular momentum. He uses Schwarzian theory as an effective description of the black hole to compute the quantum rate for massless charged scalar emission. This quantum rate is then compared to the semi-classical Hawking rate, which is the rate at which black holes emit radiation classically predicted by Stephen Hawking’s groundbreaking work.
The study classifies black holes into two categories: small and large, each with a unique spectrum of emissions. For small black holes, the emission rate below a particular quantum scale deviates from the semi-classical prediction. Depending on the energy relative to a scale associated with superradiance—a phenomenon where radiation is amplified—the emission can be mostly non-superradiant or mostly superradiant. Interestingly, the quantum rate for non-superradiant emission is suppressed compared to the semi-classical rate, similar to recent observations for neutral radiation. Conversely, for superradiant emission, the quantum rate is enhanced compared to the semi-classical rate, a novel behavior observed in this research.
For large black holes, the quantum rate simplifies to the semi-classical rate. In the limit of very large black holes, the semi-classical rate aligns with the Gibbons result, which describes Schwinger-like suppression. This unified understanding of near-extremal charged emission rates, both quantum and semi-classical, covers all sizes of black holes and all energy regimes.
The research also discusses the evaporation history of each type of black hole, from when it starts very near extremality until it leaves this regime. For near-extremal Kerr black holes, the quantum rate always reduces to the semi-classical rate, with superradiant modes dominating. This rate is computed for spin 0, 1, and 2 particles.
The practical applications of this research for the energy sector are not immediate, as it is highly theoretical. However, understanding the fundamental behavior of black holes can have broader implications for our comprehension of the universe and the laws of physics. This knowledge could potentially influence future technologies and energy solutions, although such applications are speculative at this stage. The research was published in the esteemed journal Physical Review D, a testament to its significance in the field of theoretical physics.
This article is based on research available at arXiv.